1. Field of the Invention
This invention relates to locking pliers and, more specifically to a cam incorporated into the locking assembly of the pliers.
2. Background Information
Traditional pliers have, generally, two elongated members each having a handle at one end and a jaw at the other. The members cross over each other and are coupled at a single, medial pivot in a manner similar to scissors. Locking pliers, as used herein, have at least four primary members: a first member, that is a combined jaw/handle, a second jaw member, a second handle assembly, and one or more linking members. The second jaw member is pivotally coupled to the first member adjacent to the jaw so that the jaw members may close together. The second handle assembly is pivotally coupled to the second jaw member. The linking member extends between the first handle member and the second handle assembly. More specifically, the linking member extends from the distal end of the first handle member to a location adjacent to the pivot coupling of the second jaw and second handle assembly.
Thus, the first member jaw portion and the second jaw may be moved between a first, open position and a second, closed position. The second handle and the linking member also move between respective first positions and second positions corresponding to the position of the jaws. When the components of the locking pliers are in their respective first positions, the pliers are in a first, open configuration. Similarly, when the components of the locking pliers are in their respective second positions, the pliers are in a second, closed configuration. The locking pliers typically have one or more springs structured to bias the locking pliers to the first configuration.
Locking pliers may have improved operational capabilities by reconfiguring the elements or adding additional links to provide for an enhanced closing motion. For example, in one improvement the second handle assembly may be coupled to the first member adjacent to the jaw, and, a second linking member extends from the second handle assembly to the second jaw. With this addition, the line of force acting on the second linking member/second jaw coupling is generally more tangent to the first member/second jaw pivot and, as such, enhances the force applied by the user when compared to the configuration identified above.
It is further noted that, in this configuration, the jaws have a limited range of motion. Thus, if the jaws are far apart in the first position, the jaws may not be able to close completely when the handles are moved into the second position. Alternatively, if the jaws are close together in the first position, the jaws may not be able to extend around a larger object. To overcome this disadvantage locking pliers typically have a longitudinally adjustable coupling between the linking member and the first member. That is, the first handle member portion typically has a U-shaped cross-section that acts as a channel. The distal end of the first handle member portion is closed off with a generally flat flange. A first end of the linking member is slidably disposed in the channel. The location of the linking member first end relative to the first handle member portion is typically made adjustable by having a threaded rod extend through the flange. As the threaded rod, which has an external head/handle, is moved into the first handle member portion, the location of the linking member first end is adjusted toward the first member jaw portion. Generally, the closer the linking member first end is to the first member jaw portion, the closer the jaws are when in the first position.
Further, the geometry of the linking member(s) may be structured so as to act as a toggle when the pliers move into the second, closed position. That is, as the handles are moved together, the linking member will move “over-toggle” and become locked relative to the second handle assembly. If the jaws are engaging an object, the pliers will become locked about that object. With regard to the toggle, the movement of the threaded rod adjusts the location that the linking member moves over toggle and become locked.
Thus, in operation, a user typically begins with the threaded rod extended relatively far, if not as far as possible, from the first handle member portion. In this configuration, the jaws are more separated than when the threaded rod is moved into the first handle member portion. When the user draws the handles together, the jaws close and, if the jaws were initially too far apart, the user can estimate about how far to move the threaded rod for a better, tighter fit or to set the point where the linking member moves over-toggle and locks the pliers to the object. Alternatively, a user may move the pliers into the second position around an object and then use the threaded rod, that is, insert the threaded rod into the first handle member portion, to lock the pliers in place.
The disadvantage to using a threaded rod is that manipulation of the threaded rod is slow and requires dexterity on the part of the user. Generally, the user must grasp and twist the threaded rod with their fingers. Thus, in most instances, the user must hold the pliers with one hand while manipulating the threaded rod with the other hand. This can be particularly disadvantageous when the user is, for example, attempting to grip two or more heavy objects in the jaw and then lock the jaw. In such an instance, the user must be strong and quick or the user is likely to loose their grip.